This invention relates generally to demand metering systems and more particularly to electronically controlled time of day demand metering systems for registering the amount of electrical energy consumed during specified demand time intervals of the day.
Utility companies have generally sold electrical energy on the basis of a fixed rate schedule regardless of whether high or low demand has been made upon the electrical generation system. This type of rate scheduling has not provided the consumer with the incentive to voluntarily reduce his power consumption, particularly during those periods of high peak demand. As a result, in order to prevent overloading the power distribution system, utility companies have had to add additional power generating capacity which can be brought on line during peak power periods. The addition of this power generating capacity has placed an economic burden on the utility companies as well as the consumer, as the cost of the power generating equipment must be passed on to the consumer. This is an undesirable economic burden, particularly when it is realized that the additional power generating equipment is brought on line only during those periods of high peak demand. Thus, the additional equipment is only used part time, resulting in inefficiencies since a much larger power generating plant and distribution system than is economically desirable is required in order to meet those periods of peak demand.
In the past few years, with the escalating costs of generating electrical energy, utility companies and the manufacturers of electrical energy metering systems have attempted to develop equipment and devices which will provide for more efficient use of electrical generation and power distribution facilities during both on and off peak load periods. Many of these devices have resulted in the development of multiple rate metering of electrical power consumption which adopts the philosophy that the consumer whose consumption of electrical energy is principally during on-peak demand periods should be billed at a higher rate than the consumer whose consumption is primarily during periods of low, off-peak or mid-peak periods.
This multiple rate price structuring appears to be justified when it is realized that the low demand usage customer who is billed at the same rate as the high demand usage customer, in effect subsidizes the high demand user. Differential pricing would, therefore, from a customer standpoint, appear to be more equitable. From the standpoint of the utility companies, a multiple rate pricing structure will encourage consumers of electrical power to shift their consumption of power from on-peak intervals to off-peak intervals, thus increasing the overall power distribution system efficiency and reducing the capital expenditures normally required to supply extra power generating equipment during on-peak periods.
So far as it is known, the prior art systems have employed, for the most part, conventional kilowatt-hour meters having two sets of register dials to provide a dual rate price structured billing system. One such prior art attempt to individually register different amounts of power consumed during different intervals of the day is disclosed in U.S. Pat. No. 2,139,821 to Greenwood et al. In that patent, a simplified two-stage mechanical watt meter mechanism having an associated clcok timer is disclosed. Cams on the clock timer are used to trip a mechanism which, at selected times during the day, permit the selective driving of one or the other of two sets of meter register dials so that the amount of electrical energy consumed during the various on and off peak periods of the day can be registered on the appropriate dials.
Developments subsequent to Greenwood et al by Pratt (U.S. Pat. No. 2,246,185) and Cameron (U.S. Pat. No. 2,132,256) utilized dual rate metering systems incorporating a clock which determined which set of various meters were to be activated during the various on and off peak periods. Other dual rate kilowatt-hour metering systems which exemplify representative prior art structures are disclosed in the following patents: Barstow U.S. Pat. No. 548,419; Cox U.S. Pat. No. 585,258; Qxley U.S. Pat. Nos. 591,195 and 593,852; Wilson U.S. Pat. No. 596,283; Kapp U.S. Pat. No. 597,985; Oxley U.S. Pat. No. 710,070; Mayer U.S. Pat. No. 1,078,206; Ogurpowski U.S. Pat. No. 2,415,653; Feldman et al U.S. Pat. No. 3,683,343; and Kahn U.S. Pat. No. 2,915,704.
Another prior art multiple rate structuring system is disclosed in U.S. Pat. No. 4,050,020 to Germer et al and assigned to the assignee of the present invention. This patent is directed toward an electronic time-of-day metering system which is preprogrammed to selectively activate two sets of register dials at predetermined times of the day to register the amount of power consumption during designated peak intervals (e.g. high-peak and mid-peak). The present invention is ideally suited for operation with the invention of the U.S. Pat. No. 4,050,020, comprises an improvement thereof and is incorporated specifically herein as an essential reference. Further, U.S. Patent application Ser. No. 724,040, filed Sept. 17, 1976, now U.S. Pat. No. 4,093,997 entitled "Portable Programmer for Time-of-Day Metering Register System" and assigned to the assignee of the present invention discloses a programmer for programming the meter of U.S. Pat. No. 4,050,020 and the present invention.
To further encourage consumers to utilize less power during on-peak intervals, utility companies have suggested a three rate billing structure. In that type of structure, the consumer is billed at the normal rate for his total power consumption, plus an additional amount at a higher rate for the amount of power he uses during on-peak intervals. This is just like the previously described two rate structure. However, in the three rate pricing structure, the consumer is billed still an additional amount for the amount of power he consumes in the one demand interval of maximum power consumption. For example, in a 30 day month, there may be thirty programmed on-peak periods (1 per day), with each period lasting six hours. However, during each of these periods there may be extremely high peak intervals when the demand for more energy places an overload burden on the power distribution system causing the utility company to bring additional power generating equipment on line, thus increasing the cost of power generation. It is during these extremely high peak intervals that the consumer will pay an additional amount, if his demand for power exceeds a predetermined amount as established by the utility company. However, the consumer will pay only for that amount of enrgy consumed in the one demand interval, out of all of the demand intervals, of maximum energy consumption.
There has been proposed, various types of three rate billing structured systems. One such system contemplates the use of three conventional kilowatt-hour meters interconnected through various mechanical clock and switch mechanisms. One of the meters continuously registers the total amount of consumed energy, while a second meter is engaged via the clock and switch mechanism to register the amount of energy consumed during predetermined on-peak periods. A third meter is engaged, via the clock and switch mechanism, to register the amount of energy consumed during predetermined demand intervals during the on-peak periods. The utility company, taking the various meter readings, can then bill the customer according to his usage of energy using the three rate structure. While the there meter time-of-day demand system proposed may functionally perform, it has not received wide acceptance by the utility companies due to the excess costs of three meters plus additional installation expenses.
Therefore, a need exists for a fully integrated single time-of-day demand metering system utilizing one meter which provides the full capability of implementing an easily installed and readily changeable three rate billing structure to the changing rate structures of the utility companies.
It is therefore an object of the present invention to provide an improved method and apparatus for measuring and displaying electrical power consumption on different meter displays to allow a three rate billing structure to be implemented.
It is another object to provide a time-of-day demand metering system having enhanced operating capabilities.
A further object of the invention is to provide a system for measuring the consumption of power from an electrical generation and distribution system during peak periods, during predetermined demand intervals occuring in those periods and registering the amount of energy consumed during the one period of maximum demand.
Another object is to provide a system including a programmable time-of-day demand meter having the capability of implementing a plurality of rate structured billing routines for selectively measuring and displaying the consumption of electrical energy from a power distribution system during on-peak periods and during demand intervals of various selected periods in order to encourage consumers of electrical power to shift consumption of power from on-peak to off-peak periods.
A still further object is to provide a method and apparatus in a time of day demand metering system for measuring the total consumption of electrical energy, the amount of energy consumed during prescribed peak power periods and the amount of energy consumed during the one demand interval of maximum energy consumption out of all of the peak power periods.
It is another object to provide a programmable meter in a time of day demand metering system including a method and apparatus for measuring the amount of energy consumed during predetermined peak power periods of the day and further measuring the amount of energy consumed during the one demand interval, out of a plurality of predetermined demand intervals, of maximum power demand.